At my last college reunion, a classmate, besotted already with nostalgia, came up with the term “future nostalgia.” It means longing again for the moment you’re experiencing before you even finish experiencing it.

Something like that happens to you at “Million Dollar Quartet,” a thoroughly enjoyable reconstruction of a Dec. 4, 1956, meeting of four soon-to-be legends of rock ’n’ roll in Sam Phillips’ Sun Studios in Memphis.

Those in the audience old enough to remember the careers of Johnny Cash, Jerry Lee Lewis, Carl Perkins and Elvis Presley will find themselves going back and forth between the scene on stage and memories of these men in the decades that followed.

The script, by Colin Escott and Floyd Mutrux, introduces us to Phillips (Vince Nappo), a 33-year-old, enterprising producer whose mission in life is to find raw Southern musical talent and record it. So far he has done well, particularly with Carl Perkins (James Barry), a rockabilly star of such songs as “Matchbox” and “Blue Suede Shoes.”

‘Million Dollar Quartet’

Unexpected jam

Phillips narrates the events of that night, in the moment and in flashbacks. During Perkins’ recording session, Cash (David Elkins), a brash young Lewis (Ben Goddard), and Presley (Billy Woodward) along with Presley’s girlfriend, Dyanne (Kelly Lamont), stop by and jam together, aided by a drummer and a bass player (the fine Billy Shaffer and Corey Kaiser, respectively). Even Dyanne gets in on the action, with Lamont delivering a particularly sultry “Fever.”

The get-together is not without tension as four youthful (all between 21 and 24) personalities struggle to make their next career moves. Perkins is suspicious of Lewis’ keyboard talent, fearful of being overshadowed. Presley has just signed with RCA records, and later Cash tells Phillips that he has already signed with Columbia Records. By the time the evening is over, however, peace has been restored with a toast to 1957, and a group photo is snapped. And that photo of the real participants is displayed near the end of the show, drawing appreciative oohs from the audience, which at Tuesday’s opening was engrossed and responsive throughout.

The cast, under Eric Shaeffer’s direction and Chuck Mead’s musical supervision, delivers the goods. Imitators? Sure. Each of these icons had a signature twitch or sound that the guys capture to a T: Cash’s bass, Perkins’ pickin’, Presley’s throbbing and Lewis’ piano antics. But there’s no strain to do so. They’re all first-rate musicians and — particularly with Goddard, Barry, and Lamont — solid actors. Nappo superbly creates a three-dimensional portrait of a little guy with big ideas who’s on the verge of being swallowed up by the phenomenon he has helped to create.

Favorite numbers? I like the ensemble work on “Brown-Eyed Handsome Man,” “Down by the Riverside,” and “Peace in the Valley.” Elkins scores with “I Walk the Line” and Barry with “Who Do You Love?” Despite the fact that not all of the show’s songs are the ones recorded in 1956, they are apt choices.

One reservation: The show’s final four numbers, which serve as an encore, are completely unnecessary because that photograph provides the evening’s emotional closure. And after a full night of terrific music served up so brilliantly, the extra 10 minutes or so become something of a drag.